A 2006 California law, Assembly Bill 32, obligates the state to reduce greenhouse gas (GHG) emissions to 1990 levels by 2020 (30% below business as usual), and to 80% below that level by 2050 (90% below business as usual). How is it to done? A team from UC, Berkeley, Lawrence Berkeley National Labs, and elsewhere examines this challenge in the January 6, 2012 Science.

The conclusions of Jim Williams, et al: • improvements in efficiency (doing more with less) are critical. If the increase is 1.3%/year, the amount of energy needed in 2050 will be 40% less, and achievable. This rate of improvmenent would be “historically unprecedented”.

• Electricity must be decarbonized, to below 25 grams carbon dioxide equivalent/kWh by 2050. This will be hard. Carbon capture and storage must achieve 98% reduction in GHG emissions, compared to current predictions of up to 90%.

• Only as electricity is decarbonized, other sectors must become more dependent on electricity. Much more dependent—today electricity is 15% of end-use energy, but by 2050, it will be 55%, as buildings and water are heated by electricity, and vehicles are electrified. (About 30% of transportation, long-haul freight and air, will use a combination of biofuels and fossil fuels.)

• Biofuels, such as newer technology ethanol using plant cellulose rather than sugars, or diesel made from algae, would supply 20% of transportation energy, assuming these technologies are commercialized in time.

Some numbers: • CA consumes 300 TWh electricity today (300 billion kWh, population 37 million). Under business as usual, this will increase to almost 500 TWh by 2050. To meet this goal, and replace existing supplies as they age, CA will need to supply 3,000 MW in new power each year between now and 2050, and add 100 miles of transmission capability each year. High efficiency would keep electricity levels the same, in the absence of electrifying heating and transportation.

Note: 1,000 MW is the amount of electricity provided by a 1,100 MW nuclear reactor running at just over 90% capacity factor (essentially, down time for refueling and a little maintenance). It is the amount of electricity supplied by just over 5,000 MW of solar (almost 20% capacity factor) or 3,000 MW wind (about 35% capacity factor).

• Beginning about 2020, the electrification of transportation and heating will add to electricity requirements, doubling electricity demand on the high efficiency path. Four scenarios are examined for replacing fossil energy with low-GHG electricity. All scenarios assume renewables other than large hydro will supply at least 1/3 of CA electricity. Nuclear remains at today’s levels or increases.

The high renewables scenario (3/4 renewables, and less fossil plus hydro than today), 4,000 MW needs to be added per year, more than for other scenarios because intermittents need backup capacity as well. The 4,000 MW might represent 9,000 MW wind along with backup). (To compare, Texas leads the US in wind power, with 10,000 MW.) This choice requires 600 miles of new transmission lines each year. There are a fair number of details between here and there.

The high nuclear scenario (60% nuclear, and less fossil plus hydro than in the high renewables scenario) requires 3,500 MW in new construction each year between now and 2050. That’s just over two 1,100 MW nuclear reactors/year, plus a lot of renewables. It requires 500 miles in added transmission lines/year.

In the high carbon capture and storage scenario, carbon capture and storage supplies over half of 2050 electricity. This scenario requires 3,500 MW in new construction each year, and 300 miles/year in new transmission lines, less than other mitigation scenarios, presumably because current fossil fuel plants would continue to be used.

The mixed scenario is 1/3 renewables, 1/6 nuclear, and 40% CCS. It requires the same new construction as the high nuclear and high CCS scenarios, 3,500 MW, and 400 miles in new transmission lines each year.

In terms of cost, the authors reach conclusions similar to those in The Power to Reduce CO2 Emissions: The Full Portfolio, 2009 Technical Report. Costs are “roughly comparable” and would be approximately double today’s costs. (Business as usual also has much higher costs, even in the high efficiency case. In the absence of high efficiency, just imagine what happens to prices as demand increases, and increases, and increases.) The document from Electric Power Research Institute finds the costs of nuclear less than wind and much less than solar.

All scenarios require storage capacity for the renewables, from a low of 4,000 MW storage in the high nuclear scenario to three times that in the high renewables scenario.

Other points: • Technology improvements are needed. Many.

[A]chieving the infrastructure changes described above will require major improvements in the functionality and cost of a wide array of technologies and infrastructure systems, including but not limited to cellulosic and algal biofuels, [carbon capture and storage], on-grid energy storage, electric vehicle batteries, smart charging, building shells and appliances, cement manufacturing, electric industrial boilers, agriculture and forestry practices, and source reduction/capture of high-[global warming potential] emissions from industry.

• Electric cars would face less cost variation than we see today with oil price instability, and cash flow would be domestic rather than to oil powers. However, the cost of electricity would be higher. We don’t know today what capital plus fuel costs will be for electric cars of the future.

The first point is considered important enough that James Murray and David King focused on it in Nature in January, in Climate policy: Oil’s tipping point has passed—demand of fossil fuels is rising faster than supply, so they are susceptible to large increases in price with small increases in demand. We see this now for oil; the same will be true soon for natural gas and coal. The transition away from fossil fuels will take decades, no matter how motivated we are, earlier is better than later:

Governments that fail to plan for the decline in fossil-fuel production will be faced with potentially major blows to their economies even before rising sea levels flood their coasts or crops begin to fail catastrophically.

• Non-energy sources causing climate change also must be reduced by 80% as well. Examples include cement manufacture, agriculture, and forestry.

• There will be a cost, estimated to be 0.5% of gross state product in 2020, increasing to 1.2% in 2035 and 1.3% in 2050 (about $1,200 per capita). Electrifying transportation is the most expensive item on the list. Our current market structure probably can’t make the shift fast enough, requiring “novel public-private partnerships”. Aggressive R&D could reduce the cost of low-carbon electricity perhaps 40% between 2020 and 2050, saving Californians as much as $1.5 trillion.

• Per capita GHG emissions and gross domestic product are similar to those in Japan and western Europe; what works here (if it works here) may have implications elsewhere.

The article has links and >100 pages of supporting online material for those wanting to read more. For a shorter analysis, see the LBL news release.

Karen Street has an MSEE from UC, Berkeley. She worked as an electrical engineer for a number of years before becoming a teacher of high school math and physics until 1994, when after losing much of her hearing, she left teaching. On her way to becoming a science writer, she researched the differences between coal and nuclear energy and became aware of the serious threats from climate change. Since then she has worked to raise awareness of these threats through teaching, speaking and writing. Her blog focuses on climate change impacts and major solutions, in particular nuclear power and behavior change, and on evaluating the sources of information we use.